【作者】 李婧；

【导师】 邱国跃； 马晓红；

【作者基本信息】 贵州大学 ， 电气工程（专业学位）， 2018， 硕士

【摘要】 现如今各行各业对电能需求越来越大,加上电力电子器件日趋成熟,使原本就存在的无功污染、电压闪变跌落及三相不平衡等问题更加突出。STATCOM作为无功补偿领域中最新技术能很好解决上述电能质量问题,成为广为关注研究对象。目前STATCOM装置多采用多电平技术,常见于级联星形结构、级联三角形结构和模块化多电平结构(MMC),相对于传统二电平具有模块化设计、易于扩展和输出谐波低等优点,为高压大功率领域提供技术支撑。对于补偿不平衡负载,MMC拓扑比其他两种级联结构表现更具优势,为此本文对基于MMC的STATCOM不平衡控制策略(Unbalanced Controller based on MMC-STATCOM,以下简称UCMS)进行了研究,并通过理论分析和仿真模拟,验证了所提控制策略的可行性,主要研究内容如下:首先,针对三相不平衡对传统二电平STATCOM和多电平STATCOM所造成的不同影响,说明了多电平拓扑结构不平衡控制需要考虑内特性;分析和对比了三种多电平STATCOM不平衡补偿机理,确定了本文最终采用MMC作为STATCOM的主电路拓扑结构。其次,针对现有UCMS将交流侧和内部环流分开控制的方法,结合MMC-STATCOM数学模型提出了一种基于MMC桥臂电流的STATCOM不平衡控制策略,减少环流抑制器,整体控制结构得以简化易实现。文中根据向量图阐述了理想和非理想情况下MMC-STATCOM综合补偿原理,详细介绍了装置预充电环节、直流电容电压均衡控制策略和上、下桥臂电流控制策略,其中还根据Bode图分析了参数设置对所采用陷波器和两种谐振频率(基频和倍频)准PR控制器的性能影响,并给出相应参数整定依据。最后,在EMTDC/PSCAD环境下,搭建了三相9电平MMC-STATCOM,对不平衡控制理论进行了仿真模拟,验证了本文所采用的拓扑结构和所运用的不平衡控制策略的可行性和有效性。更多还原

【Abstract】 Nowdays,the demand for electric energy is increasing in all fields,and the power electronic devices are becoming more and more mature.,which causes the existing power quality problem even worse,such as reactive power pollution,voltage fluctuation,flicker and three-phase unbalanced.As the latest technology of reactive power compensation,STATCOM can solve these power quality problems well,and has become the focus object.At present,multilevel technology is widely adopted in STATCOM devices,which is commonly used in cascade star structure,cascade triangle structure and modularized multilevel structure.Comparing with traditional two-level technology,it has the advantages of modularization design,easy expansion,low output harmonics and so on,which provides technical support for high-voltage and high-power situation.For compensating unbalanced loads,the topology of MMC is superior to the other two cascaded structures.Therefore,the unbalanced control strategy for MMC based on STATCOM(UCMS)is studied in this paper,combining with the theoretical investigation,and simulation analysis,the reliability of the unbalanced control strategy is demonstrated.The main research contents are as follows:Firstly,according to the different effects of three-phase imbalance on traditional two-level STATCOM and multilevel STATCOM,it is shown that internal unbalanced control should be considered in the multilevel topology.The performance of three multilevel STATCOM unbalanced compensation is analyzed and compared.Therefore,determination has made: the selection of the MMC chain structure.Secondly,according to the existing UCMS with the AC side and internal circulation are controlled separately and the MMC-STATCOM mathematical model,the STATCOM unbalanced controller based on MMC bridge current is proposed without a dedicated inner circulating current controller,which makes the overall control structure simple and easy to realize.This paper expounds the principle of MMC-STATCOM comprehensive compensation in ideal and non-ideal cases with vector diagrams,and the DC capacitor charging,DC capacitor voltage equalization control and strategy of the MMC bridge arm current are introduced in detail.According to the Bode diagrams,the effect of parameters setting on the performance of notch filter and two kinds of resonant frequency quasi-PR controller are analyzed,and also gives the basis of parameters tuning.Finally,a 9-level three-phase STATCOM is built in the EMTDC/PSCAD environment,and carries out the simulation of the unbalanced control theory.The simulation result verifies the feasibility and effectiveness of the topology structure and unbalanced control strategy used in this paper.更多还原